1. Field of the Invention
The present invention relates to an organic electroluminescence device having an organic layer including a light emitting layer between an anode and a cathode and a display unit including such an organic electroluminescence device.
2. Description of the Related Art
An organic electroluminescence device (so-called organic EL device) in which electroluminescence (EL) of an organic material is used has a laminated structure provided with an organic layer in which an organic hole transport layer, an organic light emitting layer and the like are layered between an anode and a cathode. The organic electroluminescence device has attracted attention as a light emitting device capable of high-intensity light emitting by low voltage direct current drive.
FIG. 16 illustrates a cross sectional structure example of a top emission type organic electroluminescence device out of the foregoing organic electroluminescence device. An organic electroluminescence device 101 has a structure in which a light reflective anode 103, an organic layer 104, and a light transmissive cathode 105 are layered in this order on a drive substrate 102 having a drive circuit such as a thin film transistor (TFT). The organic layer 104 has, for example, a structure in which a hole transport layer 104A, a light emitting layer 104B, and an electron transport layer 104C are layered sequentially from the anode 103 side.
Thereby, emitted light is allowed to be extracted from the opposite side of the drive substrate 102 including the drive circuit (cathode 105 side). Thus, such a structure is advantageous to improve the aperture ratio of the light emitting section. Since the aperture ratio is improved, sufficient light emitting luminance is obtained even if the current density applied to the organic electroluminescence device is kept low. Accordingly, it leads to improvement of the life characteristics.
Thus, in the organic electroluminescence device 101, the anode 103 provided on the drive substrate 102 side is used as a reflecting electrode, and the cathode 105 is used as a transparent or semi-transparent electrode. To effectively extract emitted light from the cathode 105 side, the anode 103 should be made a material having high reflectance.
As a material composing such an anode 103, for example, it has been proposed to use silver (Ag) or an alloy containing silver as described in, for example, Japanese Unexamined Patent Application Publication No. 2003-77681 and Japanese Unexamined Patent Application Publication No. 2003-234193. Further, it has been also proposed to use an aluminum (Al) alloy containing copper (Cu), palladium (Pd), gold (Au), nickel (Ni), or platinum (Pt) as an accessory metal as described in, for example, Japanese Unexamined Patent Application Publication No. 2003-234193. Further, it has been also proposed to use an aluminum alloy containing an element with a relatively smaller work function than that of aluminum (for example, neodymium (Nd)) as an accessory metal as described in, for example, Japanese Unexamined Patent Application Publication No. 2006-79836.
In the case where aluminum (Al) alloy is used as an anode, to cover heat resistance and hillock resistance, a material containing, for example, a rear earth element (Nd), a high-melting-point metal or the like other than Al may be adopted. Examples of such a high-melting-point metal include tantalum (Ta), titanium (Ti), nickel (Ni), tungsten (W), and silicon (Si). Specially, an AlNd-based alloy containing Al and Nd, an AlTa-based alloy, an AlNi-based alloy (for example, AlCNi alloy), or an AlSi-based alloy is adoptable more suitably.